Japan has a variety of manufacturing industries that support the foundations of industry, such as manufacturing of semiconductors, electronic equipment, precision machinery, transportation machinery, chemical products, foodstuffs and/or the like. In factories that take charge of actual manufacturing in these kinds of manufacturing industries, products are assembled through automated procedures or manual procedures while numerous parts flow along production lines.
When there are flaws or defects in parts used in manufacturing products, or when there are flaws or defects in manufacturing procedures, the products that are manufactured naturally have flaws or defects, and the problem arises that manufacturing yields decline. Or, even if there are no problems in parts, flaws or defects at times arise in products after manufacturing, for a variety of reasons. As problems relating to both the former and the latter, when operational flaws in various processes arise in automated manufacturing processes, the problems arise that manufacturing speed (manufacturing efficiency) declines and product manufacturing yields decline.
In the past, it was often the case, primarily at large companies, that the flow of processes including research, development, design, manufacturing, quality control and sales was vertically integrated. In a vertically integrated company, the response in development and design to insufficient quality or declining yields in manufactured products (finished products or semi-finished products) turned out at a manufacturing site took place in an environment in which feedback and feedforward were easy within the same company.
In contrast, in recent years companies have been spinning off manufacturing divisions (that is to say, manufacturing plants) due to problems with manufacturing costs, and manufacturing companies that undertake only subcontracted manufacturing have appeared. Similarly, fabless companies that undertake research and development alone and do not undertake manufacturing have prospered, particularly in the electric equipment field, the information communication field and/or the like.
In this manner, in manufacturing industries at present, in many cases there are physical, time, technological and human separations between the site where development and design are done and the site where actual manufacturing is done. When such separations exist, feedback and feedforward between the manufacturing site and the development site for quality deficiencies and declining yields at the manufacturing site are difficult. As a result of this difficulty, there are concerns that manufacturing capabilities are declining in Japan's manufacturing industry (including fabless companies, manufacturing subsidiaries, contract manufacturing companies that handle only manufacturing, and/or the like).
There are a variety of causes of deterioration in product quality and yields at manufacturing sites. There are inevitable causes such as simplicity in design and manufacturing, skill levels at the manufacturing site, the flow of manufacturing processes, manufacturing facilities, personal skills and/or the like, but one cause that tends to be overlooked is static electricity. That is to say, there are various causes of defects or flaws in parts, products or manufacturing processes, and one cause is thought to be static electricity.
At manufacturing plants, measures are taken so that static electricity does not have an effect on parts, products or manufacturing procedures, such as discharging electricity, preventing static electricity buildup in plant buildings, floors, walls and/or the like, and measures to prevent static electricity on workers' clothing, and/or the like, out of consideration for the negative effect of static electricity on parts, products, manufacturing procedures and/or the like. At an actual manufacturing plant, electric charge is eliminated on floors, walls, conveyor lines and/or the like prior to the start of work, and electrical grounds for eliminating electric charge are set up, but static electricity is generated inside the manufacturing plant and measures are taken to ensure that parts and products used in manufacturing procedures do not carry static electricity.
In addition, at manufacturing plants, measures are taken to discharge in advance parts used in manufacturing procedures. Similarly, measures are undertaken to ensure that workers also start work after eliminating electric charge.
In this manner, various measures have been implemented to reduce the negative effects of static electricity at manufacturing plants. Despite such measures, the problem that parts and products used in manufacturing procedures carry static electricity has not been completely resolved. For example, progress is being made in reducing power consumption by electronic equipment and precision equipment manufactured at manufacturing plants. Accompanying reductions in power consumption, parts used in manufacturing such electronic equipment and precision equipment are caused to have reduced capacity for discharging static electricity. Consequently, parts used in manufacturing such electronic equipment and precision equipment often carry static electricity and are easily damaged.
There are various types of parts used in manufacturing such electronic equipment and precision equipment. For example, numerous parts made of resin or vinyl (connectors, screen covers, housings and/or the like) are used. These parts have a certain size, and carrying static electricity, there are times when unpredictable behavior occurs. For example, a plurality of parts enter a procedure in which these parts flow along a conveyor line and are arranged at certain positions, or enter procedures for external appearance inspections by image processing. In these procedures, the plurality of parts introduced to the conveyor line preferably flow along the conveyor line with the introduced spacing maintained.
However, when such parts carry static electricity, movement is generated in the conveyor line as the parts draw closer to each other or are repelled from each other by static electricity. Depending on the case, adjacent parts could stick to each other. When such behavior occurs, the appropriate processes cannot be done in the above-described arrangement procedure or external appearance inspection procedure.
When this kind of unpredictable behavior occurs in such parts in the arrangement procedure and the external appearance inspection procedure, it is necessary to temporarily halt the conveyor line. Despite predictions that this behavior is caused by static electricity, as a countermeasure there is no alternative but to eliminate electric charge on the conveyor line, equipment for the procedures and furthermore all parts introduced to the conveyor line. When the conveyor line stops as a result of this charge-elimination work, a large loss is incurred in the manufacturing plant. That is because manufacturing work halts during the charge-elimination work (which, depending on the case, can take half a day or a full day).
It is understood that static electricity is the cause of such parts giving rise to the above-described behavior, but the mechanism leading to the actual behavior is virtually unexplained. In particular, there are times when different behaviors are exhibited, such as parts moving toward or away from each other and/or the like, and there are times when absolutely no behavior is exhibited. Consequently, explaining the mechanism leading to the behavior is difficult when it is not known how the static electricity that is (thought to be) building up on parts is distributed in the parts. If understanding the mechanism is difficult, it naturally follows that it is impossible to consider countermeasures to prevent the above-described behavior.
Or, covers made of resin, vinyl and/or the like attached to the screen of a mobile telephone handset, smartphone and/or the like readily carry static electricity based on the type of material and the size of the surface. When such parts are used in assembly procedures for electronic equipment or precision equipment, when the parts inevitably carry static electricity, there are cases in which arrangement positions arbitrarily shift because of the static electricity. When this occurs, the equipment being assembled naturally becomes flawed.
In this case as well, despite forecasts that the parts building up static electricity is the cause, the relationship between the behavior and static electricity buildup is unknown. When this relationship is unknown, it is impossible to try resolving the problem. That is to say, accurately understanding what causes this kind of buildup in static electricity is a prerequisite for resolving problems that occur in manufacturing procedures. Stated another way, in such parts, being able to confirm with what distribution static electricity is building up is a prerequisite condition for understanding the behavior of the parts.
Similarly, in equipment that uses static electricity, such as printers and/or the like, confirming static electricity distribution in parts that use static electricity buildup is necessary.
Thus, in the prerequisite of resolving various problems thought to originate from static electricity in manufacturing procedures, and in prerequisites to confirming the performance and properties of parts that use static electricity, it is desirable to measure the static electricity distribution on a part and/or the like and furthermore to make this visible.
As methods for measuring this kind of static electricity distribution, a number of technologies have been proposed (for example, see Patent Literature 1 or Patent Literature 2).